Final answer:
The most appropriate evaluation method for a customer service training program is measuring the change in the number of customer complaints before and after the training.
Step-by-step explanation:
The best measure to describe the results evaluation method of a new customer service development program is to look at the number of customer complaints measured before and after the training (Option C). This approach aligns with the results-level measurement identified in the 2003 study by Arthur, Bennett, Edens, and Bell, which includes productivity and profits as outcomes. While a 360-degree feedback process (Option A) offers a comprehensive view of an employee's performance from multiple perspectives, its reliability can vary. An online evaluation (Option B) provides immediate participant feedback, and pre- and post-training tests (Option D) assess learning outcomes, but neither directly measures the impact on organizational goals such as customer satisfaction.